It’s amazing how little the average Joe knows about water and it’s behavior. What I know has taken me years to learn. It’s a plumber’s job to know what each valve does and which size hose should be used. It’s a pond professional’s job to know specific plumbing techniques used in pond filtering systems. Water flows can determine whether equipment on the pond will perform as they should or become expensive wastes of dollars.
The Doc has a knack for such knowledge. He knows off the top of his head which pump will be best for a 15-foot waterfall and how to get the most from the filter by adjusting flows. For some of us, however, it doesn’t come that easy. One must think like water when he works with water. It’s with that thought in mind that we’ll explore the wonderful world of pond plumbing and maybe I’ll be able to explain it in a way that won’t bore us “laymen” to tears.
Use PVC When Possible
Hard PVC pipe is less expensive than black flex and lasts a lot longer. It is easy to glue together and comes in just about any size. A flexible PVC is now available in 2” and 1 1/2” diameters. Flex PVC allows curves instead of elbows that slow flow.
Bigger Diameters / Shorter Lengths
Size does matter! A small diameter hose connected to a pump will create pressure but restricts the amount of water that can flow through the hose. A larger diameter hose will make the most of the pump’s gallons per hour (gph) and create more volume. A bigger diameter is better in all cases when it comes to flow. The size of the pump outlet should not determine the size of hose to be used. For example, Cal Waterfall Pumps have 1 1/4” openings but we advise that no less than 1 1/2” hose be used on ponds up to 1200 gallons and no less than 2” hose be used on ponds larger than that. The larger sized hose can be placed on the pump by simply changing the connector.
The farther the water has to travel the less flow there will be. Use the least length of hose as possible or compensate for the loss by using a stronger pump. The loss of “head pressure” is felt strongest when the water is pushed UP. Again, compensate by selecting a strong enough pump for the lift.
Use Water Flow Rates to Increase the Effectiveness of Bead Filters
LOWER the flow rate through the bead filter to achieve the best FILTERING possible. Just because a bead filter is designed to withstand high water pressures (psi) doesn’t mean it does it’s best filtering at the higher flow rates. The optimum flow rates for normal day-in-day-out filtering is between 2500 and 3000 gph on the smaller ProBeads and 2000 to 4500 gph on the larger Ultra High Flow models.
INCREASE the flow rate through the bead filter to achieve the best BACKWASH possible. A proper backwash requires at least 4000 gph. Backwashing with less than 4000 gph on most bead filters does not do the job at all!
2-speed pumps are great for bead filters because they allow you to run normally on low and backwash on high. By installing a by-pass (tee in the line that divides the flow) before the filter, half the water or so can be diverted directly past the filter during normal filtering operation then closed off during backwashing so all the water flows through the filter.
When Slow Flows Are Desirable
Some equipment require slower flows to operate correctly. An ultraviolet water sterilizer clears the water by killing free-flowing algae. If the water passes through too quickly it will not do the job it is designed to do. Some styles of filters cannot take more than 500 gph. For example, too much pressure inside a BioForce filter will damage the unit. A gravity-fed box filter can take up to 1000 gph as long as the water exits the filter faster than it enters. Otherwise water backs up inside the box, spills over the edge and can drain a pond within hours.
If the flow needed for a waterfall is more than the equipment will handle the water must be divided by installing a tee or a by-pass to the equipment. One end of the tee would go through the equipment while the other simply returns to the pond at the top of the waterfall. Gate valves and ball valves are used to adjust the water flow to the equipment.
Water Flow and Waterfalls
Everyone has his own idea of what kind of waterfall he wants. One may want white water rapids while another might prefer a quiet sheet of cascading water or a meandering stream. Many factors are involved with determining the strength of a pump needed for the desired flow.
Here are some that must be considered:
- How wide is the waterfall or stream? It takes less water to fill 1 foot than 2 feet of space.
- How much flow is desired?
- How high and how far is the water being pumped?
- If a bead filter is in the design, where is it in proportion to the pump?
No matter what flow we are trying to achieve one factor never changes. We can’t turn UP a pump’s flow but we can turn it DOWN. If there is a decision to be made between two strengths of pumps it’s always best to go with the strongest.